Let katanas delimb the person holding them

[zjdtmkhzt]

Leaving aside whether or not the katana deserves this (pretty miniscule) nerf, I think that an important thing to keep in mind here is things being consistent. None of the other melee weapons or anything have random rules that mainly seem to come into play when hitting yourself, why should the katana?
If a person replaces their arm with a katana and I know that disarming or pushing a person with an item arm down will make them hit themself, I would assume that they would have a chance to delimb themselves. This being arbitrarily disabled seems very strange to me.